Your Digest for Saturday, Dec 30, 2023 10:59 PM


Aetiology: incompletely understood; malazzesia proliferation may play a role along with many other risk factors.


PrimaryDyslipidaemias.jpg

Can be divided into the following:

  1. Combined hyperlipidaemia

    1. commonest type of disorder
    2. FCHL - very common (==1/200==) (familial combined hyperlipidaemia)
      1. phenotype: ↑ TGL +/- ↑ LDL-c + suppression of HDL
      2. It is diagnosed by finding raised cholesterol and triglyceride concentrations in association with a typical family history. No physical signs.
      3. Note that familial doesn't mean monogenic.
    3. Remnant hyperilidaemia - another cause of combined hyperlipidaemia:
      1. Patients have increased IDL remnants.
      2. Extreme cardiovasular risk
      3. Pathognomonic physical signs: palmar xanthomata a dn tuberose xanthomata (over knees and elbows)
  2. Disorders of chylomicrons and VLDL -
    2. commonest - polygenic hypertriglyceridaemia. ("vast majority" of hypertriglyceridaemia patients are polygenic.) Patients have modest elevations in triglycerides.
    1. Rarely, severe hypertriglyceridemia is caused by monogenic inheritance. (but not necessarily autosomal dominant)

    1. lipoprotein lipase deficiencies - accumulation of chylomicrons in blood -> massive hyperlipidaemia (can see lipid layer in serum samples)
      1. mnemonic; two Ls in lipoprotein lipase and two Ls in lipid layer
  3. disorders of LDL -
    2. Heterozygous familial hypercholesterolaemia (HeFH) -
    1. #autosomalDominant
    2. Defective LDL receptor
    3. mild to severe lipid derangement (==1/350== incidence)
    4. Mutations mainly affect the LDLR receptor.
    5. Can have physical signs including xanthomas.

    1. Homozygous familial hypercholesterolaemia (HoFH) - HUGELY elevated LDL-C (==1/250,000== incidence). Most die of ischemic heart disease by age 35

      1. Presents in children.
      2. Also caused by defective LDL receptor.
      3. Poor response to statins.
      4. Liver transplantation can normalize lipid levels. (?introduces hepatocytes with functioning LDL receptors)
    2. Mutations in the apoB and PCSK9 genes - same presentation as HeFH, but milder. Only way to differentiate it genetic tests. - relatively common

    3. Polygenic hypercholesterolaemia - no single identifiable gene deffect but have moderately elevated cholesterol levels.

  4. disorders of HDL - rare


See [[passMedicine Summaries#Evaluation of gradual visual loss]]

visualFields.png

[!TIP] Mnemonic: RIFC: retina - ipsi, Field - contra

See also:

[!INFO] Retrochiasmal lesions will cause contralateral homonymous visual field defects.
According to the figure above, temporal lobe lesions will cause a contralateral superior quadrantonopia.
These are "Meyer's loop" lesions.


| Hyphema | Retinal detachment |

Evaluation of gradual visual loss

[!INFO] Visual loss means loss of one or more of

Pearls


Central Vs. Peripheral vision loss:


Speed of onset

Leading causes of blindness

Retinal vessel occlusion

bloodSupplyOftheEye.png
Source

Retinal artery occlusion (RAO) Retinal Venous occlusion (RVO)
Less common Much more common
Older population older population
Urgent need of further evaluation Doesn't need further evaluation for cause
Higher risk of ASCVD events
Managed by neurologist - like a stroke Managed by ophthalmologist
Permanent renal death in a few hours.
Commonest causes are emboli:
+ ICA emobli
+ aortic arch, cardiac
Sudden vision loss (curtain coming down) Vision loss ranges from slight to severe
Retinal haemorrhages are common
Vascular causes are the main risk factors Age seems to be the main risk factor
Source